Commercially available expandable automation devices (also known as programmable logic controllers) or expandable automation devices described in patent documents can be adapted to a wide variety of automation tasks and are used, in particular, in the field of industrial automation technology and in the field of switching and control technology.
These automation systems are usually constructed in modular form from a central subassembly, communication couplers and expansion modules, for example input/output modules.
According to the known prior art, the input/output modules which are electrically connected to a central subassembly having the central processing unit (CPU) via an internal bus connection in the form of an input/output bus comprise a separable housing which comprises two parts and has at least one front cover, connection terminals and display means for displaying the current operating state of a switching and/or control module assigned to the respective connection terminal (also referred to as signalling the state of the input/output channels).
Input/output modules, in the housing lower part of which a plurality of printed circuit boards are inserted into a housing lower part, are known according to the prior art. Electronic subassemblies for input/output functions, connection terminals and display means, for example for displaying the current operating state of a switching and/or control module assigned to the respective connection terminal, are arranged on the printed circuit boards in the input/output modules. The connection terminals are electrically connected to the printed circuit boards according to their function and are routed out of the housing on the rear part of the housing lower part. The connection terminals are therefore not accessible from the front side of the module which has the display means.
Owing to the mechanical design, in particular the use of a plurality of printed circuit boards for implementing the functions of the input/output module, the previously described input/output module requires a considerable amount of space and is complicated and costly to produce.